Basically i have an amplifier with output resistor and a rectifier so that i can feed the output to LCD voltmeter. Now do i need a output resistor from only positive output from rectifier or negative output as well?

If your voltmeter can do AC then it can simply be placed across the load resistor. The one load resistor is enough.

Otherwise, place the diode's anode between the capacitor and the load resistor, and add a capacitor to ground tied to the cathode. That will give you a positive voltage on the capacitor. The capacitor will smooth out the DC so the voltmeter gives a steady reading.

If your voltmeter can do AC then it can simply be placed across the load resistor. The one load resistor is enough.

Otherwise, place the diode's anode between the capacitor and the load resistor, and add a capacitor to ground tied to the cathode. That will give you a positive voltage on the capacitor. The capacitor will smooth out the DC so the voltmeter gives a steady reading.